Does anyone recognise a pattern in the DSO traces that could explain what is going on here?
I recognize that something is wrong with your project yes. If you would like to know what that something might be, then ask someone who can see your wiring and your code. This would have been a GREAT place to post it since there are lots of people here who could look at it for you. Why you chose to hide the one piece of information that is most important to helping you is beyond me.
Do you not want someone to help you figure this out?